Latch systems are commonly used on sliding doors for trucks. In the first generation of such systems, the handle assembly is mounted on the sliding door and includes inner and outer handles pivoting on a common axis. Pivotal actuation of either handle concurrently actuated forwardly extending and rearwardly extending pivotal latches. These latches cooperated with horizontally extending strike bars mounted to the front and rear posts of the door frame.
The first generation sliding door latch system had several operational disadvantages. For example, if either handle was pivoted toward the receiving post at the time the door reached either a fully closed or fully opened position, the pivotal latch was not in an operative position to complete the latch. Thus, the actuated handle had to be returned to its neutral position before the door was fully closed or fully opened in order for a proper latch to be completed to retain the door in the selected position. Moreover, the horizontal strike bars mounted on the front and rear posts of the door frame extended into the door opening to reduce clearance for ingress and egress. This reduction in clearance was undesirable because people leave and enter the truck carrying loads requiring as much clearance as possible. In addition, the strike bar being horizontally mounted limited vertical freedom or flexibility for the sliding door when in its closed and latched position. Some vertical freedom for the door is desirable to minimize the chances of the door seizing in the slide tracks.
Improvements were made in this first generation system, as shown for example in U.S. Pat. No. 4,126,340. In such patent, the handle assembly includes an inner mechanism allowing the front latch to be pivotally actuated independently of the back latch and vice versa.
In a second generation system, the handle assembly on the sliding door had inner and outer pivotal handles coaxially mounted and selectively actuated to operate front or back rotary latches through an internal gear mechanism. This second generation system suffered many of the same disadvantages as a number of the first generation system. Specifically, if either handle remained in its pivotal actuation position at the conclusion of the sliding door movement, the door would not properly latch shut or open. In addition, the horizontal strike bars on the front and back door frame posts reduced door opening clearance and limited freedom for vertical movement of the door in the latched condition.